DETROIT (AP) -- U.S. safety regulators are investigating complaints that power-assisted brakes can fail at times in Camry gas-electric hybrids.

The probe covers about 30,000 of the midsize cars from the 2007 and 2008 model years.

The National Highway Traffic Safety Administration says it has 59 complaints about intermittent loss of power-brake assist. The agency says the problem happens without warning. It causes increased stopping distances and requires more pedal pressure to stop the car.

Two crashes have been reported but no injuries. The agency says 24 incidents happened at speeds of 40 miles (65 kilometers) per hour or more. It says the number of complaints is increasing, with 55 percent received in the past eight months.

Investigators will try to find the cause and determine if the cars should be recalled.